1. Field of the Invention
The present invention relates to a flat panel display (FPD), and more particularly, to an FPD with a reduced time required to change images between frames by improving waveforms of a selection signal and a drive signal for driving the FPD.
2. Discussion of the Background
An electrophoretic display (EPD), a type of FPD, is a non-self light-emitting display that uses electrophoresis affecting charged particles suspended in a solvent to display an image.
Generally, an EPD includes a pair of opposing substrates which are separated from each other. The substrates each include an electrode, at least one of which is transparent. An electrophoretic device is interposed between the opposing substrates, and the electrophoretic device includes a dielectric solvent and charged particles dispersed in the dielectric solvent.
When different voltages are applied across the two electrodes, the charged particles move toward the electrode with polarity opposite to the polarity of the charged particles. The color of the image formed on the EPD is determined by the color of the dielectric solvent, the color of the charged particles, and the arrangement of the charged particles within the dielectric solvent.
The EPD transmits a selection signal and a data signal to pixels in a pixel region through scanning lines and data signal lines, respectively, to generate a predetermined grayscale image. A pixel is formed in the pixel region where a scanning line and a data signal line cross with each other in the pixel region. The data signal transmitted to each pixel can be controlled by a transistor device, which can be a thin film transistor (TFT).
FIG. 1 is a drive waveform for driving a conventional FPD.
To generate an image by controlling the arrangement of charged particles in an electrophoretic device, a frame includes a shake section, an image-loading section, and a bi-stable state section as illustrated in FIG. 1.
In the shake section, the charged particles are repeatedly and alternatingly moved between the two electrodes to remove an image generated in a previous frame.
The shake section is followed by the image-loading section, in which the charged particles are arranged to generate an image. The image-loading section includes a driver section, in which data is entered, and a pre-drive section occurring before the drive section.
In the pre-drive section, a data signal with the same magnitude and opposite polarity of the data signal in the drive section is transmitted to the pixel electrodes. Thus, a negative image is generated in the pre-drive section. This allows the grayscale image to be generated more accurately. Next, during the drive section, a data signal having predetermined grayscale information is transmitted to the pixel electrodes. As a result, a desired image is generated in the pixels of the EPD.
The image-loading section is followed by the bi-stable state section, in which the charged particles are stabilized and the arrangement of the charged particles within the dielectric solvent is maintained. Accordingly, the generated image is maintained for a predetermined period of time after the data is entered. In the bi-stable section, the selection signal and the data signal transmitted to the pixels are turned off, thereby reducing power consumption.
Generally, the selection signal transmitted to the pixels through the scanning lines S[1] through S[n] during the shake section and the image-loading section is a pulse signal having a predetermined positive voltage Vs and a predetermined negative voltage −Vs. To generate a desired image, the data signal Va and −Va transmitted to the pixels through the data signal lines D[1] through D[m] includes information regarding a desired arrangement of the charged particles in the electrophoretic cell. The information may be affected by the magnitude of the predetermined positive voltage and predetermined negative voltage.
Alternatively, an image may be generated by transmitting a signal having different pulse widths to the pixels using a pulse width modulation (PWM) method or by changing the number of pulses applied to the pixels during one frame.
However, according to a drive waveform for driving the conventional EPD, the selection signal is transmitted as an alternating pulse signal in the shake section. However, it is not necessary to selectively transmit the data signal to the pixels during the shake section. As a result, power consumption is increased unnecessarily.
In addition, the length of the shake section must last a predetermined duration to remove an image generated in a previous frame.
To generate an image, the pre-drive section and the drive section are required. However, when data is entered with a conventional drive waveform but without a pre-drive section, it is difficult to generate an accurate grayscale image. Therefore, the conventional EPD with a conventional drive waveform as illustrated in FIG. 1 requires time to change images in successive frames.